1. Field of the Invention
This invention relates generally to communications networks, and more particularly to methods and associated systems for establishing a session in a mobile network.
2. Description of the Background Art
Mobile systems such as cellular phones and wireless data communications devices allow a user to communicate with other users or access remote computers from any location within a roaming zone. The freedom and convenience afforded by mobile systems have made them very popular.
The growth of the Internet has created a demand for mobile systems that can provide e-mail and Internet connectivity in addition to telephone service. This is to be expected as the Internet is rich with information and allows access to a wide variety of on-line services. Unfortunately, data communications on the Internet is conducted using the Internet Protocol (IP), which transports packets on a best-effort basis. That is, the IP protocol does not have mechanisms for guaranteeing a certain level of quality of service (QoS), such as delay, throughput, jitter, etc. This creates a problem because some sessions require a higher level of QoS than others. For example, a multimedia session ordinarily requires a higher bandwidth and lower delay than a web browsing session. Despite this limitation of IP, mobile networks continue to migrate towards IP-based architectures not just to provide Internet connectivity, but also to take advantage of IP routers which cost lower than traditional mobile switches. In an IP-based mobile network, a mobile station is coupled to a base station controller, which in turn is attached to a node of an IP network.
Protocols such as the Resource Reservation Setup Protocol (RSVP) and Multiprotocol Label Switching (MPLS) have been developed to guarantee a certain level of QoS in an IP network. RSVP defines a convention for transferring QoS requirements to nodes within the IP network. Using RSVP, resources along a traffic route can be allocated for a particular session. Thereafter, MPLS methods, which make use of path-forwarding and QoS information, may be employed to transport the session""s packets along the traffic route. The application is thus guaranteed a level of QoS as long as the traffic route does not change, which is usually the case with fixed IP networks.
Because mobile stations can move from one location to another, mobile networks present a set of problems not ordinarily encountered in fixed IP networks. For example, when an originating mobile station initiates a video telephone session to a terminating mobile station, resources along a route between the originating and terminating mobile stations are allocated using RSVP to guarantee the session a level of QoS. However, moving the originating (or terminating) mobile station to another location changes part of the route, resulting in new nodes along the new route. Because resources have not been allocated for the video telephone session on the new nodes, QoS can no longer be guaranteed. Further, the movement of the originating mobile station changes the total traffic on the nodes along the new and old routes, making it difficult to keep track of the overall traffic and resource usage on the IP network. Unfortunately, existing conventions for routing packets in a mobile IP network, such as Mobile IP, do not adequately address the aforementioned problems.
The present invention relates to a method and associated system for establishing a session with a level of quality of service (QoS) in a mobile network. In one embodiment, a session for a mobile station is established by finding a route and determining the availability of resources on the route. Thereafter, active per-hop behaviors (PHB""s) are distributed to ports along the route. Additionally, inactive PHB""s are distributed to ports near the route. The active and inactive PHB""s provide information on how to route, transport, and process packets belonging to the session. In one embodiment, each of the PHB""s indicates a priority level, forwarding port number, rules for discarding packets, rules for sending packets, etc. The packets are transported from one port to another in accordance with the active PHB""s, thereby guaranteeing a level of QoS. When the mobile station moves to a new location and changes the route, inactive PHB""s are activated on the new route. This not only allows mobile stations to communicate at a certain level of QoS even after a move, but also minimizes the delay resulting from the move.
These and other features and advantages of the present invention will be readily apparent to persons of ordinary skill in the art upon reading the entirety of this disclosure, which includes the accompanying drawings and claims.